Skeletal Muscle Contraction Flashcards Preview

physiology (Woods) > Skeletal Muscle Contraction > Flashcards

Flashcards in Skeletal Muscle Contraction Deck (37):
1

define epimysium

connective tissue surrounding entire muscle

2

define muscle

made up of multiple fascicles (each containing fiber)

3

define perimysium

connective tissue surrounding individual fascicle (typically thinner than epimysium)

4

define fascicle

a bundle of myofibers

5

define endomysium

delicate connective tissue around each myofiber

6

define sarcolemma (=plasmalemma)

cell membrane of muscle fiber

7

define myofiber (=muscle cell)

individual multinucleate muscle cell

8

define myofibril

chain of sarcomeres within a myofiber (intracellular configuration)

9

define myofilament

actin and myosin filaments that make up a sarcomere

10

what does sarco mean in greek

flesh

11

what are T-tubules

*invaginations of sarcolemma
* live close to cistern of SR
*form triads with cistern
*2 per sarcomere

12

what are Z discs (lines)

anchor actin filaments
located at each of a sarcomere

13

what are I bands

composed of entirely actin
width changes during contraction
reflection of light

14

what are A bands

composed of actin and myosin
width does not change during contraction
reflection of light

15

what are H bands

composed entirely of myosin
width changes during contraction

16

what are the short-hand steps of muscle contraction

1. action potential in alpha motor neuron
2. Ca++ influx into axon terminal
3. exocytosis of synaptic vesicles
4. acetylcholine release into synaptic cleft
5. diffusion of Ach across cleft
6. binding of Ach to Ach receptors on sarcolemma
7. opening of ligand-gated Na+ channels
8. Na+ influx
9. end-plate depolarization
10. opening of voltage-gated Na+ channels
11. sarcolemma action potential
12. depolarization fo T-tubules
13. Conformational change in DHP receptors
14. conformational change in ryanodine receptors
15. opening of ryanodine Ca++ channels
16. release of Ca++ from SR
17. Ca+ concentration in cytosol increases
18. binding of Ca++ to Troponin
19. Conformational change in troponin
20. tropomyosin is pulled away from active sites on actin
21. exposure of actin sites on actin
22. binding of myosin heads to actin active sites

17

what are characteristics of DHP receptors

* voltage-sensitive L-type Ca++ channels arranged in quadruplets
* located on the sarcolemma T-tubules
* cause a conformational change in the ryanodine receptors

18

what are characteristics of ryanodine receptors

* located on the cisternae of SR
* open in response to conformational change in DHP receptors
* allow Ca++ into the cytosol from the SR
* SERCA uses ATP to pump calcium back into the SR

19

define preload

load on a muscle in the relaxed state before in contracts

20

what are the types of tension

passive: produced by pre-load
active: produced by cross-bridging
total: sum of active and passive tension

21

where is ATP required for muscle contraction

* most used for the sliding filament mechanism
* pumping Ca++ from Sarcoplasm back into SR
* pumping sodium and K+ through the sarcolemma to re-restablish resting potential

22

What is phosphocreatine

*releases energy rapidly
* reconstitutes ATP

23

compare isometric and isotonic contractions

isometric occurs when there is an increase in tension but not length while isotonic is when muscle length changes (lengthens=eccentric, shortens=concentric)

24

compare white and red muscle fibers:

white are more rapid, have fewer mitochondria, primarily are anaerobic, little myoglobin and larger concentration of ATPase when compared to red

25

what is soleus

muscles predominantly composed of dark fibers

26

what is gastrocnemius

muscle predominantly composed of light fibers

27

what is the difference between first-class, second-class, and 3rd class lever systems?

first class: fulcrum is in the middle (in force and out first move in opposite directions)
2nd class: resistance (outforce) is in the middle): both in and out forces are on the same side of the fulcrum
3rd: efforce (in force) is in the middle (both forces move in same direction)

28

what is referred to as a chain of sarcomeres

myofibril

29

which sarcoplasmic band does not undergo a change in length during the contraction of a skeletal muscle

A band

30

which sarcomeric band is composed entirely of actin filaments

I band

31

DHP channels are part of what structure

T tubules

32

Ryanodine sensitive calcium ion release channels is part of what structure

SR

33

what factor does the concentration of calcium increase in the cytosol after released from the SR

100

34

what helps maintain the optimum calcium concentration gradient to facilitate return of calcium to SR

calsequestrin

35

what is an example of eccentric contraction

the tricep muscle while lowering the body to the floor during a push up

36

what is anchored to the presynaptic membrane and associated with synaptic vesicles to which they are tethered by short filaments

dense bar

37

In order for acetylcholine-gated ion channels to open, how much Ach molecules are necessary to attach its alpha subunit

2